Fig. 3: Extracellular activation of TREK-2 by Nb-Activator-67.
A Crystal structure of TREK-2 in complex with Nb-Activator-67 (Nb67). Nanobodies bind to each side of the Cap ___domain and on one side (green subunit) the Cap helix unwinds. A third Nb67 (grey) is also found in the asymmetric unit bound to the intracellular surface. These unusual features may arise from the tetramerisation of Nb67 within the crystal (see Supplementary Fig. 4A). B Dose-response relationships showing extracellular activation of TREK-2 channel activity by Nb67. Whole-cell TREK-2 currents were recorded at +40 mV and perfused with different concentrations of Nb67. Currents were normalised to those recorded prior to the application of nanobody. No activation of TRAAK or TALK-2 K2P channels was observed, but for the related TREK-1 up to 50% inhibition of channel activity was seen at concentrations of Nb67 > 1 µM. (Error bars represent mean ± S.D; n ≥ 3). C Expanded view of the interaction of Nb67 with the two sides of the Cap ___domain. The interaction with Nb67A (Left) shows no distortion of the helices, whereas interaction with N67B on the opposite side results in unwinding of EH1B (residues E113, E116 and D120 are unique in TREK-2 vs TREK-1). Right: the interaction of N108 with NB67B differs on the side where EH1B is unwound. This interaction does not occur with Nb67A.
